A crust of blood had already formed on Vassily Grodnikov's crushed skull by the time his brother broke down the door of his cottage and found his corpse.

The 67-year old writer had got drunk and fallen on his head, prosecutors in Belarus later concluded. "It's absurd," says Mr Grodnikov's brother, Nikolai, who shakes with fear at speaking openly for the first time about the death. "The postmortem showed there wasn't a drop of alcohol in his body."

As Europe wakes up to the Kremlin's stranglehold on its natural gas supplies, a stark light has been shone on how the Russian president, Vladimir Putin, does business with the other independent states that once made up the Soviet Union.

Moscow's demand for Ukraine to pay a fivefold increase for deliveries of Russian gas earlier this month was widely seen as punishment for Kiev's push to join the European Union and Nato since its "orange revolution" last winter.

What is less known is the flip side to this gritty political game: the Kremlin is propping up a despotic pro-Moscow regime on the edge of Europe that only survives because it gets extremely cheap gas from Russia.

Belarus - wedged between its giant neighbour and Poland - looks and feels like a microcosm of the old Soviet Union, complete with bad suits, big squares and ruthless KGB oppression. It is run by President Alexander Lukashenko, a paternalistic hardliner who brooks no dissent.

"Lukashenko has put fear into this country in a way that hasn't been seen since Stalin," says the Belarussian opposition leader, Alexander Milinkevich, a physicist who plots strategy against his nemesis in a mouldering apartment in the suburbs of the capital, Minsk. "He wouldn't last a month without Putin giving him cheap energy."

Lukashenko uses the crushing weight of an 80% state-run economy to exert almost total control, says Milinkevich. Gas supplies from Russia at $47 per 1,000 cubic metres (compared to the $230 market price that Moscow demanded from Ukraine) keep Soviet-era factories creaking along. And there are no inconvenient oligarchs to fund the opposition.

But while Belarus's GDP is on the rise, the eerily spotless streets and facades of Minsk conceal a dirty underworld of persecution, killings and disappearances.

Mr Grodnikov's alleged murder comes as Lukashenko's hardline regime twists a tourniquet on the slightest sign of dissent in the run up to presidential elections on March 19.

The writer's body was discovered recently at the cottage outside Minsk where he wrote articles about state corruption for Belarus's last surviving daily independent newspaper, Narodnaya Volya (People's Will).

His brother, Nikolai, thinks he knows why he died. "They killed him because they are terrified of a revolution, and he found out about their plans to squash any protest," he said.

Guardian Unlimited has learned Mr Grodnikov was investigating rumours of police plans to secretly detain opposition activists at a dacha settlement for senior interior ministry officials near the capital. He died on the day he planned to go to the settlement. State prosecutors refused to investigate.

Since Lukashenko - who is known as Batka (Daddy) - came to power in 1994, a series of politicians and journalists have been imprisoned, killed, or simply disappeared.

As a result, the United States and European Union countries are trying to crank up pressure on Lukashenko ahead of the presidential poll in March.

The US secretary of state, Condoleezza Rice, has called for Belarus "to throw off the yoke of tyranny" and Britain is taking a confrontational stance, with ambassador Brian Bennett accusing Lukashenko of leading "a slide into dictatorship".

One senior western diplomat in Minsk confirmed that foreign experts are being drafted in to "help [opposition] parties with their organisation, and showing them how democracy works, how to get in touch with the people".

It is a tricky pursuit, as paranoia grows in Russia and Belarus about western "meddling" in their internal affairs. The two countries have a union with each other, military cooperation is strong and their peoples are practically inseparable in terms of national identity. Moscow supports the Minsk regime because it wants to preserve it as a buffer zone against Nato encroachment.

Lukashenko, meanwhile, has warned foreign states to keep their noses out of the election.

Last month, his simpering "parliament" made it a crime to discredit the country by passing "false information" to a foreign state or organisation about its political, economic or legal situation. The popular uprisings in other former Soviet states were "simple banditry, deftly carried out with western money", Lukashenko claims.

Observers say the president was rattled by the rose revolution in Georgia in 2003 and the orange revolution in Ukraine in 2004. "He's worried," said the diplomat. "He knows he can engineer 80% of the vote in his favour, but he's forming special police units to break up crowds, just in case."

The opposition faces a huge task to oust Europe's pariah. Anti-Lukashenko parties have not a single seat in parliament and most have been denied registration. Independent press is being hounded out of existence. And because of his grip on the state-run economy, Lukashenko's opponents can be cowed with threats of being sacked and never working again.

Milinkevich, the opposition leader who is due to meet senior EU officials today, is seen as the only hope for change, but his profile is low because he is denied exposure in state media.

"I'm placing my hopes in the younger generation," says the scientist, who heads a loose coalition of democratic forces and will stand for the presidency. Underground youth movements like Zubr (Bison) are small, but their numbers are swelling as increasing numbers of students are expelled from university for dabbling in politics.

"If the presidential election is falsified, we will go the streets to protect our rights," says Nikita Sasim, 21, a Zubr leader who says he was hospitalised with concussion after police beat him at a recent protest.

Yet the opposition know its chances are slim. Lukashenko dominates television broadcasts and is riding high in official polls with an almost trance-like power over many of his compatriots.

"He is an excellent example in all areas," says Sergei Yuran, 45, an engineer, shuffling through snow in central Minsk. Ludmila Yolkina, a music teacher, says: "We don't want all that civil unrest like in Ukraine. Look at our ordered city and nice clean streets."

The gas crisis made western Europe question President Putin's democratic credentials as he took over the presidency of the G8. His support for Batka could be the next big point of confrontation.